Combination of base isolation and diagonal perimeter frame

This paperpresents anoverviewof the structuraldesignofa20-storeyoffice buildingwithabase isolation which considerably reduces seismic load of the superstructure. The structural members are designed to remain elastic during an earthquake of 500-year return period. The inner rigid frame with typical beam spans 15 m × 25.5 m, providing flexible office spaces within the building. As a result, the main columns experience significant axial forces under long-term loading, requiring them to be placed upon single isolator unit comprised of 4 individual rubber bearings. Due to the large stiffness in the diagonal perimeter frame, which intersects at every three floors, most of the seismic forces are transmitted by these structural members. Coinciding with the exterior double skin facade system for airflow ventilation, this diagonal module has proved to be most fitting, both architecturally and structurally. The combination of a base isolation system and the diagonal perimeter frame, achieves low response accelerations about 100 gals on typical floors and story drifts lower than 1/500 in an earthquake of 500-year return period. This not only protects the life safety during a large earthquake but also assures the building to be fully functional, secures the properties within the structure, and benefits the architectural intent of a transparent facade glazing.